The invention relates to an electrical machine having a stator and a rotor, with the rotor having a plurality of axially arranged cooling channels and a first and a second end face, and with a fan unit being arranged on each end face and comprising at least two fan segments, with one fan segment in each case being associated with one cooling channel and being arranged alternately on the first end face and on the second end face.
Heat losses occur during operation of electrical machines, and must be appropriately dissipated. It is known for electrical machines, in particular of a closed type, to be equipped with internal cooling circuits which ensure appropriate cooling by equalizing out the temperature differences in the interior of the machine.
DE 42 42 132 A1 discloses a closed electrical machine in which an internal fan is arranged on the rotor shaft on each of the two end faces of its rotor and rotor cooling channels, which extend over the entire axial length of the rotor laminated core, are provided in the rotor laminated core. Flow passes through the rotor cooling channels either from the drive end to the non-drive end or vice versa, that is to say the flow takes place in opposite directions. The internal fans are in the form of integral radial fans, and are arranged directly on the rotor shaft.
DE 616 902 discloses a cooling arrangement for rotors for completely closed electrical machines, in which the rotor is cooled by circulating air flows which are passed alternately through axial channels in a different direction and are moved by fans on the end faces of the rotor, with fans being arranged on both end faces of the machine and being provided in their hub part with channels which are used to guide the air flows.
One disadvantage in this case is that the fans can be used only for electrical machines of one specific size, since they are formed integrally. Other fans must accordingly be used for electrical machines of other sizes.
DE 470 020 discloses a cooling arrangement for rotors of a completely closed type, in which the cooling air is sucked by vanes, which are fitted to the end surfaces of the rotor, through axial channels in the rotor from the drive end to the non-drive end, and vice versa.